The avoidance of shock loads caused by the take-up of slack between cooperating elements of a coupling system through which draft and buff loads are applied to a train has long been a concern of railway operators. In some dedicated train operations it is advantageous to avoid the weight and cost of standard AAR couplers and draft gear by replacing them with light weight, simple drawbars but this means that slack take-up and impact dissipation systems included in the deleted equipment are also eliminated. Therefore it has been a goal in designing drawbar systems to eliminate slack. It is also desirable to keep the apparatus light in weight, strong enough to withstand maximum draft and buff loads and flexible enough to handle side to side and fore and aft angling as required by AAR rules.
Slackless systems have been provided before. For example, U.S. Pat. No. 4,580,686 illustrates a wedge-shaped slack take-up member and U.S. Pat. No. 4,996,291 shows a rotary drawbar system. The disclosures of the above patents are incorporated herein by reference and made a part of this disclosure.